An Overview of Choroideremia

Choroideremia is a rare inherited disorder that causes progressive vision loss, ultimately leading to complete blindness. Choroideremia mainly affects males due to its X-linked etiology. The condition is also known by the names choroidal sclerosis and progressive tapetochoroidal dystrophy.

Choroideremia affects about one in 50,000 to 100,000 people and accounts for around 4% of blindness. Because its symptoms are very similar to other eye disorders, the condition is thought to be underdiagnosed.

Symptoms

The first symptom of choroideremia is the development of night blindness (poor vision in the dark). This usually occurs during childhood. Some males, however, do not notice reduced night vision until the mid-to-late teens. Night blindness is followed by a loss of mid-periphery vision and a decrease in the ability to see details.

Blind spots begin to appear in an irregular ring, leaving small patches of vision in the periphery, while central vision is still maintained. As the disease progresses, peripheral vision loss worsens, leading to “tunnel vision.”

Loss of color vision can also occur as degeneration of the macula takes place. Eventually, the vision is completely lost.

Causes

The gene that causes choroideremia is located on the X chromosome, so the condition is diagnosed almost exclusively in men, although female carriers can occasionally present with symptoms that are much milder. Choroideremia affects the retina, the thin layer of tissue that lines the back of the eye on the inside. Mutations in the choroideremia gene cause the cells of the retina to die prematurely.

Diagnosis

Eye doctors use several tests in order to properly diagnose choroideremia. When a young patient complains of night vision loss, a comprehensive eye exam is recommended to check for signs of the condition. Diagnosis of choroideremia can be confirmed by symptoms, test results, and a family history consistent with genetic inheritance.

• Fundus examination: A fundus exam may reveal patchy areas of chorioretinal degeneration in the mid-periphery of the fundus. These changes in the fundus are followed by a noticeable ring scotoma, an area of blindness noted during a visual field test.
• Electroretinogram (ERG): An electroretinogram may show a degeneration pattern in the rods and cones.
• Fluorescein Angiography: This test may reveal areas of damage in the fovea.
• Fundus Autofluorescence: Testing can show areas of atrophy within the fundus.
• OCT: OCT exam may reveal an increase in retinal thickness in the early course of the disease but can progressively thin out as the disease advances.
• Genetic testing: Genetic tests are used to confirm the presence of choroideremia gene mutation.

Treatment

At this time, there is no treatment or cure for choroideremia. As the disease progresses, further vision problems may develop. Additional treatments may be needed if other vision issues develop, such as cataracts and retinal swelling. While nothing can be done to stop or reverse retinal degeneration with choroideremia, there are steps that can be taken to slow the rate of vision loss.

Doctors suggest adding plenty of fresh fruits and green leafy vegetables to the diet. Antioxidant vitamin supplements are also recommended, along with regular intake of foods rich in omega-3 fatty acids. Lutein has also been identified as a supplement to reduce the progression of atrophy and vision loss in choroideremia. Wearing sunglasses with UV protection is also highly recommended.

Recent success in the treatment of certain genetic disorders has brought hope for developing a successful treatment for choroideremia. Since choroideremia is a genetic disease and caused by a mutation of one gene, it is a promising candidate for successful gene therapy. Another potential treatment that may help to restore vision after it has been lost later in life is stem cell therapy.

Coping

Dealing with major vision loss has been compared to the "stages of grief" experienced after the loss of a loved one. A person may start with denial and anger after diagnosis, then progress to depression, and finally, to acceptance.

Understanding the various stages of the disease will help you understand your feelings, as well as ease your fears. Remember that more than three million people in the United States aged 40 years and over are legally blind or living with low vision. Reach out to others experiencing vision loss for support, advice, and encouragement.

A Word From Verywell

While there is currently no known cure for choroideremia, the disease is a good target for gene therapy and there are new studies underway that are examining gene therapy options for treatment. These studies are encouraging and will hopefully present a way to treat patients in the near future.

The Choroideremia Research Foundation provides support for individuals with choroideremia and raises money for further research.